Airless spray gun utilizing low pressure coating material source



Dec. 29, 1964 J. H. M NINCH, JR.. ETAL 3,163,350

AIRLESS SP Y GUN UTILIZING LOW PRESSURE C0 NG MATERIAL SOURCE 2 Sheets-Sheet 1 Filed Dec. 26, 1962 INVENTOR. H. MCNINCH JR. J- DELLA FLORA gosEPH OBER'I' BY Dec. 29, 1964 J. H. M NINCH, JR.. ETAL 3,163,350

AIRLESS SPRAY GUN UTILIZING LOW PRESSURE COATING MATERIAL SOURCE 2 Sheets-Sheet 2 Filed Dec. 26, 1962 IIIF I I I l i I 'AIIII INVENTOR. JOSEPH H. MCNlNCl-IJR. Ica-sawr J. DELLA FLORA ATT ORN EYS United States Patent 3,163,360 AIRLESS SPRAY GUN UTELIZLJG LQW PRESSURE CGATEJG MATERHAL SQURQE doseph H. McNinch, Jan, and Robert '3'. Della Flora,

Toledo, ()hio, assiglors to The De Vilbiss Company,

Toledo, Uhio, a corporation of Uhio Filed Dec. 26, 1962, Ser. No. 246,979 12 Claims. (Cl. 239124) This invention relates to an airless spray gun which employs coating material from a relatively low pressure source and more particularly to a spray gun which, using low pressure coating material, raises the pressure of the material within the spray gun and ejects it as a finely atomized airless spray therefrom.

Spray guns capable of atomizing coating material without air are known in the art. Such spray guns provide good control over the coating material and substantially reduce overspray, which is inherent in the spraying operation when air is employed. With airless spray guns heretofore known, the coating material is placed under high pressure by a pump or other device located at a distance from the spray gun. Consequently, the pressure creating device, the hose and other portions of thesystem contain high pressure material and the systems are expensive because heavy, high quality hoses, pumps, tanks and other equipment are needed to create and contain the high pressure coating material.

The spray gun according to the present invention atomizes coating material by high pressure and without air and takes the coating material from a relatively low pressure source and increases the pressure only after the material has entered the spray gun. Consequently, only an ordinary low pressure source and hose equipment are required for the over-all coating system. The pressure of the coating material within the gun is raised by air or other suitable fluid under very moderate pressure sup plied to the spray gun from a conventional air compressor. piston assembly which enables the pressure of the coating material to be raised to a level higher than that of the fluid driving the piston assembly. The coating material is ejected by one portion of the piston assembly in rapid pulses which provide a substantially continuous flow of atomized coating particles.

it is, therefore, a principal object of the invention to provide an airless spray gun which requires only a low pressure on the coating material, and which eliminates the usual high pressure source and associated heavy hoses and other equipment.

Other objects and advantages ofthe invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a schematic view in elevation of a spray gun.

This is accomplished by means of a reciprocating almost continuous spray when the trigger is pulled.

a main air line 18, a coating material line 20, and a relatively low pressure source 22 of coating material or paint.

The material in the container 22 is placed under pressure by airsupplied through a line 24 from a storage tank 26' and a compressor 28.

Coating material from the. source 22 is fed through the line 2% to an inlet passage 39 (FIG. 2) in the spray gun body 12. The inlet passage 3t) communicates witha large annular chamber 31, which serves .as a surge chamber, and an annular manifold 32. The latter is associated with a supply opening or ports 34 which are blocked by a check valve ring 36 which is urged to a closed position by a suitable spring 38. The opening 34, the ring 36, and the. spring 38 constitutes check valve means by which coating material can enter a coating material chamber or cylinder extension 40 and a coating material cylinder 42. from the source 22, but cannot flow in the reverse direction.

The coating material is drawn into the chamber and cylinder when a coating'material piston 44 is retracted or moved rearwardly to reduce the pressure in the chamher and cylinder under that of the coating material in the inlet 30. This pressure ditierence overcomes the force of the spring 38, moving the ring 36 away from the ports 34-, so that the chamber 48 and the cylinder 42 are filled with coating material upon opening of the check valve ring 36. When the piston 44 moves forwardly again, the coating material in the chamber 40 and the cylinder 42 is placed under increasingly high pressure until the pressure becomes sufiicient to overcome the force of a spring 46 and to move a pressure valve member 48 away from its seat 49 (as shown) within the group of outlet passages 50 communicating with the chamber 40- This occurs very quickly in the forward motion of the piston and the coating material flows through the outlet passages 59, a central outlet passage 52 in the member 48 and, hence, through a nozzle cap 54. The nozzle can be designed according to high pressure spray nozzles known in the art and does not constitute a novel part of in a suitable retaining chamber 56 which is ventedthrough a line to the coating material supply so that leakage around the valve member 48 will'not be a problem.

From the above, it will be apparent that the coating material is supplied through the outlet passage 52 in pulses, one during each cycle of the coating material p1ston 44, which pulses are so frequent as to establish an It can be seen that the off time during which no paint is being discharged will determine the gaps in a spray Patented Dec. 23, 1964 a I supply, again flowing through the annular supply manitold 32. By opening the valve 6%, a greater quantity of the coating material can flow from the chamber 40,

part of it flowing back through thepassage as and the.

return line 68 to the supply manifold 32. This effectively increases the available discharge areathrough which paint 1 can flow, which results in a greater speed of operation of the piston and an increase in the frequency of operation, as well as a reduction of the fon time of thedevice.

However, all of the coating material which does flow past the valve member 48 is at the same pressure, regardless of the degree to which the liquid control valve 643 is opened.

The coating material piston 44, is connected through a stem 76 to an intermediate or return piston 72 which is functionally integral with a power piston 74, the latter being provided with a suitable piston ring 76. The power piston 74 is located within a power cylinder 78 having an end wall 79 through which a'portion of the intermediate piston 72 extends. The power piston 7% drives the coating material piston 44 forwardly when air or other suitable power fluid is applied to the'rear of the power cylinder 78. The air supply for the power cylinder is'provided through a controlled air supply passage 8i? which is regulated by the trigger in and is connected to the air line 18. The passage 80 communicates with an air manifold 82 which has a plurality of passages 84 connecting the manifold 82 witha small annular valve chamber as adjacent a valve plate 88. The valve plate 38 has two positions, a rear one in which it contacts an exhaust valve seat 90, as shown, and a forward one in which it contacts a fluid power valve seat 92.

With the valve plate 88 in the rear position, the air in the small valve chamber 36 can flow between the valve plate 88 and the second valve seat 92 and, hence, into the rear of the cylinder 73. The piston 74 then moves forwardly in the cylinder 78 until the piston ring 76 moves beyond exhaust ports 9 located around the wall of the cylinder 78, which ports communicate :with an exhaust manifold 96 and cylinder exhaust passages 58 vented when the edge of the piston 74 has moved forwardly to open the exhaust ports 94. The trigger-controlled air supplied through the passages 34 is then blocked from flowing between the valve seat 92 and the valve plate As the valve plate 88 moves against the valve seat 92, it also moves away from the valve seat 90, so that air in the rear portion of the cylinder 78 can be'exhausted through rearexhaust ports 112, passages 114, and exhaust outletslilS as the piston 74 moves rearwardly. This release of air continues until the edge of the piston 74 moves over the rear set of exhaust ports 112 whereupon remaining air between the valve plate 83 and the power piston 74 is trapped. Further movement of the piston 74 builds up the pressure in the working cylinder 78 and causes the valve plate 88 to move again to its rear position against the valve seat 90.

As soon as the valve plate 33 has been forced to its rear position, power fluid from the line 34 again is supand are effective to exhaust fluid from the cylinder 78 a when the piston 74 has moved forwardly a predetermined distance. When the piston ring 76' moves beyond the ports 94, the air remaining in the end of the cylinder 73 is compressed and acts as a cushion for the piston 74,

helping it tobounce back, thus aiding in bringing about the return stroke of the entire piston assembly. However,"

the major portion of the energy for the return stroke of the main power piston 74 is provided by air in an intermediate chamber 169 in which the intermediate piston 72 reciprocates, which air acts on the annular end of the piston 72 and urgesit, along with the piston 74, rearwardly. t.

The air for the chamber 1% is supplied through a passage 102 and a line 1'34 from a supply line 106 which communicates directly with the line 13. The supply line tee is not controlled by the trigger 16 so that air pressure always exists in the chamber 1% and always urges the intermediate piston 72 and the entire'piston assembly rearwardly, even when the trigger 16 is in the off position Vent passages 107 are also formed in the gun body to accommodate the pumping action of the piston 44 and to vent any leakage of air or coating material from cylinders 42 and ltlii.

An'air chamber llild is located behind the valve plate 88 and is also supplied with line air from the supply line 1% through a suitable tube lit The air pressure in the chamber 138 urges the valve plate 88 forwardly and moves it against the seat 97; after the cylinder 78 has been air from the passages 34.

plied to the rear end of the cylinder 78 to again drive the piston 74 forwardly, the exhaust ports 112 now being blocked by the valve plate 88 and the valve seat 9%. Once again, the piston 74 moves forwardly until theedge of the piston 74 moves beyond the forward'exhaust ports 94, whereupon the drop in pressure in the cylinder 78 enables the air pressure in the air chamber 1% to move the valve plate 8% forwardly and thus block the flow of the supply The cylinder 78 then remains vented by means of the rear exhaust ports 112 commu nicating with the exhaust passages 114 and the exhaust outlets 115 until the piston 74 again reaches a rear position where the piston 74 covers or moves beyond the ports 112.

To review the overall operation of the spray gun 10,

when spraying is to be initiated, air from the tank 26 is supplied to the source .22 to place the coating material therein under pressure. The material, under a pressure of 100 pounds per square inch, for example, is then fed through the line 26 to the inlet passage 3%) and the surge chamber 31. At the same time, line air is supplied through the line 18 and the supply line 166 to' thelines 1&2 and 164 and to the intermediate chamber 109. The air pressure in the chamber 1% then acts on the intermediate piston 72 and moves the main piston 74 to the rear position, if not already there. The air from the sup ply line 1% is also 'transmitted through the tubes 110 to the air chamber 168 which urges the plate 88 toward the front position against the valve seat 92. a

Assuming that the-paint cylinder 42 has been primed,

the spray gun 10 is now incondition to spray coating material when the trigger 16 is'pulled. When this is done, air is supplied through the passage 80, the manifold 82, and the passages 84 to the annular chamber 86 at the outer edge of the plate 88, this air also having a tendency tomove the plate 88 to the rear position. A bleed hole 116 allows sufiicient air to bleed into'the power cylinder 78 to assure that the valve plate 88 will be up. The air passes between the valve seat 92 and the plate $8 into the rear of the power cylinder 7 8. This'air cannot escape through the exhaust ports 112 because the exhaust passage 1E4 communicating therewith is blocked by the seal effected through contact of the valve plate 83 with the valve seat 96. Hence, the air supplied to the rear of the cylinder 78 pushes the power piston 74 forwardly until the edge of the piston ring 76 uncovers the exhaust ports d4 whereupon the power air 'is.-.vented through the exhaust passages 98. vValve 83 moves immediately to its forward position against seat 92 by means of the pressure in the chamber 108. v

cylinder 42 and forces coating material in the cylinder 42 and the chamber 40 to move through the passages 50, past the valve member 48, and out of the orifice in the cap 54, when the coating material reaches suflicient pressure to overcome the force of the spring 46. By way of example, the spring 46 is designed to prevent the valve member 48 from opening until the pressure of the coating material exceeds 900 pounds per square inch. Hence, the pressure of the'coating material is raised from its inlet or supply pressure of approximately 100 pounds per square inch to at least 900 pounds per square inch when it is'forced into the spray gun nozzle opening and out of the spray cap.

To regulate the quantity of coating material sprayed through the nozzle, while retaining it under the same pressure, the needle .62 is backed away from, or closed in towards, the valve seat 64 so that a greater or less quantity of the coating material in the chamber 40 and the cylinder 42 is recirculated through the passages 66 and 68 and into the supply manifold 52.

At this time, the exhaust ports 94 have exhausted air in the rear portion of the chamber 74 with the air pressure in the valve chamber 108 forcing the valve plate 88 forwardly. This has stopped the flow of the air from the manifold 82 and at the same time the exhaust ports 112 and the exhaust passages 114 to the rear exhaust ports 115 have been opened. Hence, .air in the cylinder 78 is exhausted through the ports 112 during the rearward stroke of the piston 74. After the coating material piston 44 and the power piston '74 have reached the forward end of their strokes, they reverse and move toward the rear, due to the bounce force of the compressed air trapped in the front of the main cylinder 78 and the air bias on piston 72 in cylinder 100. 7

After the edge of the piston ring 75 moves rearwardly beyond the ports 112, the remaining air in the working cylinder 78 is trapped between the plate 88 and the piston 74, and as the pressure of the trapped air increases and its force exceeds the force of the air in the chamber 108 the plate 83 is forced to the rear position to open the air supply passages 84 which again reverses the direction of the piston 74. The piston 74 is then ready for another cycle.

During the reverse movement of the piston 74, the coating material piston 44 also is retracted in the cylinder 42, thereby admitting coating material through the check valve ports 34 and past the check valve ring 36 into the chamber 40 and the cylinder 42. Another cycle of the spraying operation also is then ready to commence. In practice, the pistons operate at a rate of 2000 to 6000 cycles per minute.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and tenor of the accompanying claims.

What we claim is:

1. An airless spray gun comprising. a spray gun body having therein a power cylinder and a coating material cylinder, a coating material piston in said coatingmaterial cylinder, a power piston in said power cylinder and having means connecting said power piston to said coating material piston, a valve plate at a rear portion of said power .cylinder opposite the coating material cylinder, passage means in said spray gun body connected to the rear end of said power cylinder, means for supplying power fluid to said passage means, means forming a fluid control valve seat associated with said passage means and positioned to be engaged by said valve plate to prevent the flow of power fluid into said power cylinder from said passage means, means eifective to urge said valve plate toward said valve seat, a rear exhaust port in said body located near the rear end of said power cylinder and effective to trap power fluid between said valve plate and said power piston when said rear exhaust port is blocked as said power piston moves in a rearward direction, a rear exhaust passage communicating with said exhaust port, 1 means forming an exhaust valve seat positioned to block said rear exhaust passage when contacted by said valveplate, additional exhaust means efiective to exhaust power fluid from said power cylinder when said power piston has moved forwardly in said cylinder a predetermined distance, means located-outside said power cylinder cooperating with said connecting means between said powerpiston and said coating material piston to urge said power piston toward the rear of said power cylinder, coating material supply means communicating with said coating material cylinder, check valve means enabling the flow of coating material from said coating material supply means into said coating material cylinder and blocking the flow of coating material in the reverse direction, an outlet port in said body communicating with said coating material cylinder, nozzle means connected with said outlet port, a pressure valve member blocking said outlet port, means urging said pressure valve member toward the blocking position, said urging means being yieldable to enable said pressure valve member to move to an open position when pressure of the coating material within said coating material cylinder rises above a predetermined amount, whereby coating material can flow to said nozzle means under high pressure.

2. An airless spray gun accordingto claim l wherein said additional exhaust means includes a forward exhaust port in said gun body located near the front end of said power cylinder and spaced from the front end a distance such that fluid is trapped between said power piston and said front end when said power piston passes said forward exhaust port when moving in a forward direction.

3. An airless spray gun according to claim 1 characterized by means for adjusting the coating material output of said spray gun.

4. An airless spray gun according to claim 3 wherein said output adjusting means includes recirculating passage means communicating with said coating material cylinder and said coating material supply means, and valve means in said recirculating passage means, said valve means being adjustable to control the amount of coating material which is recirculated from said coating materialcylinder back to said coating material supply means. 7

5. An airless spray gun comprising a spray gun body having a coating material cylinder, a coating material pis ton reciprocable in said cylinder, power means connected to said piston for reciprocating the same, coating ma-' terial supply means communicating with said coating'rnaterial cylinder, check valve means enabling the flow of coating material from said supply means into said coat-' ing material cylinder and blocking the flow of coating material in the reverse direction, an outlet port in said body; communicating with said coating material cylinder, noz- 4 gun without changing the length of the stroke of said 7 coating material piston.

6. An airless spray gun comprising a spray gun body having a coating material cylinder, a coating material piston reciprocable in'said cylinder, power means connected to said piston for reciprocating the same, a coating material supply passage communicating with said power cylinder as said power piston move rearwardly of said rear exhaust port, additional exhaust means effective to exhaust power fluid from said power cylinder to said nozzle means through said outlet passage means when the pressure of coating material in said cylinder is below a predetermined. amount, said pressure means enabling the flow of coating material from said cylinder to said nozzle means when the pressure of the coating material exceeds the predetermined amount, recirculating passage means insaid gun body connecting said cylinder with said supply passage, and regulating means in said recirculating passage to control the flow of coating material therethrough from said cylinder to said supply passage.

7. An airless spray gun comprising a spray gun body having a power cylinder, a power piston located in said .power cylinder, coating material spray means including coating material pressurizing means located outside said power cylinder, means extending through anend wall of a front end of said power cylinder and connecting said power piston to a portion of said pressurizing means, a 'valve plate at a rear portion of said power cylinder opposite the end wall, passage means in said spray gun body connected tothe rear portion-of said power cylinder, means for supplying power fluid to said passage means, means forming a valve seat associated with said passage means and positioned to be engaged by said valve plate to prevent the flow of power fluid into said power cylinder from said passage means, means efiective to urge said valve plate toward said valve seat independently of the position of said power piston, a rear exhaust port in said body located near the rear end of said power cylinder and effective to trap power fluid between said valve plate and said power piston when said rear exhaust port is blocked as said power piston moves in a rearward direction, a rear exhaust passage communicating with said exhaust port, means forming an additional valve seat positioned to close said rear exhaust passage when contacted by said valve plate, additional exhaust means. effective to exhaust power fluid from saidpower cylinder when said power piston has moved forwardly in said cylinder a predetermined distance, means located outside said cylinder beyond said end wall and cooperating with said connecting means between said piston and said pressurizing means to urge saidpiston toward the rear end of said power cylinder, and. trigger means for controlling the supply of power fluid to said passage means. I

8. An airless spray gun comprising a spray gun body having a power cylinder, a power piston located in said power cylinder,.'coating material spray means including coating material pressurizing means located outside said power cylinder, meansconnecting said power piston to a portion of said pressurizing means, valve means at a rear end of said power cylinder opposite said'pressurizing means, passage means in said. spraygun body connected to the rear end of said power cylinder, means body located near the rear end of saidpower cylinder, a

rear exhaust passage communicating with said exhaust port, means forming an additional valve seat positioned to be engaged by said valve means and to close said rear exhaust passage, said valve means being forced against said additional valve seat by pressure trapped in said when said power piston has moved forwardly in said cylinder a predetermined distance, and trigger means for controlling the supply of power fluid to said passage means.

9. An airless spray gun comprising a spray gun body 7. having a power cylinder, a power piston located in said power cylinder, coating material spray means including coating material pressurizing means located outside said power cylinder, stem means extending through an end wall of a front end of said power cylinder and connecting said power piston to a portion of said pressurizing means,

said stem means forming intermediate piston means, an

intermediate chamber formed by said gun body beyond the end wall of said power cylinder and enclosing said intermediate piston means, passage means in said spray gun body, connected to the rear end of said power cylinder, means for supplying power fluid to said passage means, valve means associated with said passage means for controlling the flow of power fluid from said passage means to said power cylinder, said valve means being opened when said piston is near the rear end of said cylinder, rear exhaust passage means in said body located near the rear. end of said power cylinder, second valve means located in said exhaust passage means and being open when said power piston is moving in a rearward direction, a forward exhaust port in said gun body located nearthe front, end of said cylinder and pos tioned to communicate with that portion of said power cylinder behind said power piston as said power piston nears the forward end of its stroke, and additional supply passage means communicating with said intermediate chamber for supplying power fluid thereto to act on said intermediate piston means and to urge said power piston toward the rear end of said power cylinder.

10.. An airless spray gun comprising a spray gun body having a power cylinder, a power piston located in said power cylinder, coating material spray means including coating material pressurizing means located outside said power cylinder, stem means extending through an end wall of a front end of said power cylinder and connecting said power piston to a portion of said pressurizing means, passage means in saidspray gun body connected to the rear end of said power cylinder, means for supplying power tluid to said'passage means, valve means associated with said passage means for controlling the flow of power fluid from said passage means to said power cylinder, said valve means being opened when said piston is' near the rear end of said cylinder, rear exhaust passage means in said body located near the rear end of said power cylinder, second valve means located in said exhaust passage means and being open when said power piston is moving in a rearward direction and additional exhaust means effective to exhaust power fluid from that portion of said power cylinder behind said power piston when said power piston has moved forwardly in said cylinder a predetermined distance.

11. An airless spray gun comprising a spray gun body having a power cylinder, a power piston located insaid power cylinder, coating material spray means including coating material pressurizing means located outside said power cylinder, means connecting said power cylinder to said pressurizing means, passage means in said spray gun body connected to the rear end portion of said power cylinder, means forsupplying power fluid to said passage means, fluid valve means associated with said passage means to regulate flow of power fluid to saidlpowercylinder, rear exhaust port means'in said body communicating with the rear end portion of said power cylinder, exhaust valve means for opening and closing said rear exhaust port, additional exhaust means for said power cylinder and opened when said power piston travels forwardly a predetermined distance in said power cylinder to exhaust pressure from that portion of said power cylinder to the rear of said power piston, and means for controlling said fluid valve means to control the supply of power fluid to said power cylinder.

12. An airless spray gun according to claim 6 wherein said regulating means includes a control knob extending out of said gun body for manipulation by an operator. 10

UNITED STATES PATENTS Keller Aug. 13, 1912 Stafford et a1. Mar. 6, 1934 Olches July 21, 1942 Pyles June 8, 1948 Szczep-anski June 21, 1960 FOREIGN PATENTS Switzerland Jan. 2, 1939 

5. AN AIRLESS SPRAY GUN COMPRISING A SPRAY GUN BODY HAVING A COATING MATERIAL CYLINDER, A COATING MATERIAL PISTON RECIPROCABLE IN SAID CYLINDER, POWER MEANS CONNECTED TO SAID PISTON FOR RECIPROCATING THE SAME, COATING MATERIAL SUPPLY MEANS COMMUNICATING WITH SAID COATING MATERIAL CYLINDER, CHECK VALVE MEANS ENABLING THE FLOW OF COATING MATERIAL FROM SAID SUPPLY MEANS INTO SAID COATING MATERIAL CYLINDER AND BLOCKING THE FLOW OF COATING MATERIAL IN THE REVERSE DIRECTION, AN OUTLET PORT IN SAID BODY COMMUNICATING WITH SAID COATING MATERIAL CYLINDER, NOZZLE MEANS CONNECTED WITH SAID OUTLET PORT, A PRESSURE VALVE MEMBER BETWEEN SAID OUTLET PORT AND SAID NOZZLE MEANS AND CONTROLLING FLOW OF COATING MATERIAL TO SAID NOZZLE MEANS, URGING SAID PRESSURE VALVE MEMBER TO A CLOSED POSITION, SAID URGING MEANS BEING YIELDABLE TO ENABLE SAID PRESSURE VALVE MEMBER TO MOVE TO AN OPEN POSITION WHEN PRESSURE OF THE COATING MATERIAL IN SAID COATING MATERIAL CYLINDER RISES ABOVE A PREDETERMINED AMOUNT, WHEREBY COATING MATERIAL CAN FLOW TO SAID NOZZLE MEANS UNDER HIGH PRESSURE, AND MEANS IN SAID SPRAY GUN BODY TO CHANGE THE COATING MATERIAL OUTPUT OF SAID SPRAY GUN WITHOUT CHANGING THE LENGTH OF THE STROKE OF SAID COATING MATERIAL PISTON. 